It is the third confirmed case of A/H1N1 flu on the Chinese mainland, according to the ministry.

Fang Laiying (C), dirctor of Beijing Municipal Health Bureau, Deng Ying (R), dirctor of Beijing Municipal Center for Disease Control and Prevention, and Mao Yu (L), president of Beijing Ditan Hospital, hold a press conference in Beijing, capital of China, May 16, 2009. One confirmed case of A/H1N1 flu was reported in Beijing, China's Ministry of Health said on Saturday evening. (Xinhua/Li Wen) Photo Gallery>>>

    The case involved a 18-year-old female who studies in a university in the New York State of the United States, which was the one reported previously as suspected case by the Emergency Management Office of Beijing Municipal Government Saturday evening.

    She was currently in a stable condition, with a normal body temperature, the ministry said.

    The female, a Beijing native, arrived in Beijing on May 11 on board the U.S. Continental Airline C089 and reached home accompanied by her mother, said the ministry.

A staff member casts away the exposure suit after disinfection work at Beijing Ditan Hospital, Beijing, China, May 17, 2009. One confirmed case of A/H1N1 flu was reported in Beijing, China's Ministry of Health said on Saturday evening. (Xinhua/Xing Guangli) Photo Gallery>>>

    She did not go out or meet friends after arriving home, according to the ministry's investigation.

    She felt unwell and physically weak in the noon on May 12 and took her temperature herself.

    She went to the fever outpatient section of the Peking University First Hospital in the evening on May 14 and said she developed symptoms of cough, a few sputum, headache, sore throat, chest distress and sore muscle, with a body temperature of 37.7 degrees Celsius.

A staff member guards outside the inpatient department at Beijing Ditan Hospital, Beijing, China, May 17, 2009. One confirmed case of A/H1N1 flu was reported in Beijing, China's Ministry of Health said on Saturday evening. (Xinhua/Xing Guangli) Photo Gallery>>>

    She was initially diagnosed as fever, needing further check and "suspected of A/H1N1 flu," the ministry said.

    The patient was transferred to the Beijing Ditan Hospital early in the morning on May 15.

    The Beijing Center for Disease Control and Prevention (CDC) tested a specimen taken via a swab from her throat, which showed she was "suspected positive" for A/H1N1 and positive for PIV-H3.

    The China CDC and the Chinese Academy of Medical Sciences tested the specimen again the next day and confirmed she had contracted the A/H1N1 virus.

    The ministry said experts made the decision based on the patient's symptoms, epidemiological investigation results and laboratory tests.

    All the people who had close contact with her had been tracked down and put under medical observation, with no one feeling unwell, it said.

    According to Beijing Municipal Health Bureau, Liu had only contacted with two persons, one is her mother and the other is the taxi driver who carried her to Peking University First Hospital.

    Neither of the two had shown flu symptoms, said Deng Ying, director of Beijing CDC.

    Expressing his appreciation of the 18-year-old Liu for keeping a clear diary about her journey in Beijing, Fang Laiying, director of Beijing Municipal Health Bureau, said, "she even kept the receipt from the taxi driver, otherwise it would be difficult for us to find out the driver,"

    "The quarantine hospital had arranged three doctors and three nurses for Liu and took strict medical observation on her," said Mao Yu, president of Beijing Ditan Hospital.

    "Liu is in stable condition as her temperature is getting normal and her appetite getting better," Mao said.

    The health ministry has reported the case to the World Health Organization, Hong Kong, Macao and Taiwan and relevant countries.

    The first two cases in mainland China are Chinese nationals, Bao and Lu, who had been students in the United States and Canada, and were traveling back to their homes in the past days of the month, contracted the flu strain and developed symptoms shortly after they set foot in China.